In order to radiate heat generated from semiconductor elements, base plates are joined to circuit boards to which semiconductor elements have been mounted and furthermore, heat dissipation components such as radiating fins are joined to the opposite plate surfaces of the base plates. Aluminum or composites comprising aluminum alloys and silicon carbide, having high thermal conductivity and thermal expansion coefficients close to that of the circuit boards to which they are joined, are used as base plates for such a purpose (Patent Document 1).
When using flat base plates for the above purpose, the stress generated due to the difference in the thermal expansion coefficient of the base plates and the circuit boards when the two are joined or the stress generated when packaging with resin sealants, etc. thereafter causes the base plate surface side in close contact with the radiating fins, etc. to warp concavely, and sufficient adhesion cannot be obtained when fixing radiating fins to base plates.
As means to solve this problem, there is art directed to warping the plate surface of base plates that are joined to radiating fins, etc. into convex shapes ahead of time (Patent Document 2).
Patent Document 1 JP H05-507030 A
Patent Document 2 JP H11-330308 A